The invention relates to an axle measurement holder device to fasten a measuring head to the rim of a vehicle wheel.
An axle measurement holder device of the type at issue is known from the company brochure "PROVAC," Edition 1996, of Siege Social et Agence France Sud, 16 Premiere rue, Z1-BP 127-13744 Vitrolles cedex. It features a base body consisting of two parallel bars, at the ends of which are attachment heads for the attachment to a rim of a vehicle wheel. The bars are provided with two arms arranged in a diametrically opposed manner, featuring hooks to hook into the tread of the tire at their ends that are directed radially outward. The ends of the arms directed radially inward are attached, by means of a pivot bearing, to a one armed lever that essentially faces axially away from the base body, the other end of which is connected via an articulation to a holding device arranged on the bars. The arms are acted upon by springs that act radially inward. The one armed levers can be tensed toward the inside by means of clamping devices. As a result of this tension, the one armed levers are swiveled toward the inside and the articulated radial inner ends of the arms are thereby moved radially toward the inside. In doing so the hooks at the ends of the arms are also moved radially toward the inside, so that the hooks hook into the tread of a tire. Since the pivot bearings of the arms are in a plane which is axially distant from the plane in which the hooks are located, an axial force as well as a radial force are created by means of the tension resulting from the clamping devices, said force pulling the base body toward the rim.
One disadvantage of this known axle measurement holder device resides in the fact that before and during tensioning the arms and therefore also the hooks are not symmetrized, i.e. they are in an undefined pivot position. This creates the danger that the hooks will not hook in the same plane perpendicular to the axle, with the consequence that the axle measurement holder device is not pulled to the rim in the proper axial position, whereby at the same time the axial tension force of the arms will be different. Measurement mistakes may arise in this manner, which can only be partially prevented by controlled manual clamping of the axle measurement device with the precise control of the hooking locations of the hooks. But this procedure is clumsy.
The invention has the basic task of creating an axle measurement holder device of the type including a base body for contact with the rim of a vehicle wheel and two diametrically oppositely arranged arms which have hooks on their ends directed radially outward for the purpose of hooking onto the tread of a tire and which at their ends which are directed radially inward, are respectively articulated by means of a bearing to an end of a one armed lever that is directed away from the base body, and the other end of which is connected to the base body by means of an articulation and a compression spring and by clamping means by means of which the one armed levers can be tensed radially inward, which is easy to operate and nevertheless facilitates the precise positioning and attachment of the axle measurement holder device to the rim of a vehicle wheel.
The task which is the basis for the invention is accomplished by the fact that the one armed levers are respectively preloaded radially outward by means of centering springs which exert the same forces and have the same characteristics and are supported on a central point of the base body.
The basic concept of this teaching consists of assuring a symmetrical alignment of the one armed levers in any clamping position relative to the center of the axle measurement holder device, by providing two springs that exert the same force and which have the same characteristics, supported at a central point of the base body and, in addition, pressing radially toward the outside against the one armed levers. The tensioning devices are thereby positioned symmetrically in any clamping position relative to the central point and thereby to the axle of the axle measurement holder device, with the consequence that the tension by the clamping devices is also accomplished symmetrically.
A further development of the invention resides in having the clamping devices feature a diametrically arranged rotatable threaded bar with two oppositely directed threaded sections, each of which is in operational connection with a complementary female thread in a journal which is connected in a rotating manner to the one armed lever between its articulations, around an axis which is parallel to the pivot axis of the articulation of the one armed lever. The springs are coil springs that are arranged on the threaded sections and that are supported on a stop on the threaded bar on the end directed radially outward, and the other end is supported on a central block on the base body. This embodiment is particularly simple and, moreover, includes the advantage that the stops may be formed by nuts on the threaded sections, by means of which the symmetrical alignment of the one armed levers can be achieved.
The arms are advantageously formed of bell cranks, the other arms of which are connected via articulations to the tension springs which are constructed as compression springs, the other ends of which are connected to the base body via articulations. This arrangement, according to a further development of this form of embodiment, can be implemented such that the one armed levers and the tension springs designed as compression springs, respectively, form a parallel guide.
According to one embodiment of the invention there are at least two groups of parallel axis bore holes in the base body positioned on different circles having different diameters and/or in varying number and at the same circumferential distance. A group of contact pins of the same length can be inserted into the bore holes. In this manner the attachment points defined by the ends of the contact pins can be allocated to defined contact points on the rim or holes in the rim or spaces between the spokes of the rim, so that they extend through the holes or intermediate spaces and can contact a brake disc arranged behind the rim by means of their ends, said brake disc representing an exact reference plane, and thereby assuring a parallel holding device of the axle measurement holder.
In order to be able to easily locate the bore holes that belong to one group the bore holes, according to a further development of this embodiment, feature a depression at the ends opposite the insertion points, whereby the depressions of one group of centering bore holes look alike, while the depressions of different groups of bore holes appear different. The depressions at the bore holes may feature different shapes and/or depths and/or diameters to create differing appearances. Expediently, they may also feature a different color. Regarding the shape of the depressions, a radial strip design is advantageous.